Projectile



July 11, 1961 DUNLAP ETAL 2,991,720

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NNNNNNN Rs HENRY F. DUNLAP BYGIMRES E HABLU 72 E L July 11, 1961 H. F. DUNLAP ETA]. 2,991,720

PROJECTILE Filed June 30, 1944 2 Sheets-Sheet 2 INVENTORS I'IE'IVR Y F. DUN]. AP

BY GHAREiE. LUTZE'L AT RNEY Patented July 11, 1961 2,991,720 PROJECTILE Henry F. Dunlap and Charles E. Hablutzel, Albuquerque, N. Mex., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed June 30, 1944, Ser. No. 543,003 1 Claim. (Cl. 102-83) This invention relates to projectiles for guns "and more particularly to subcaliber sabot-projectiles adapted to attain high velocities when fired from a gun.

One object of this invention is the provision of a projectile comprising a subcaliber core and a full caliber absot and bourrelet which release automatically from the core when the projectile emerges from the gun muzzle, with relatively low energy loss. The new projectile is light in weight as compared with ordinary standard projectiles and presents a substantially full caliber rear surface to pressures developed in the gun barrel.

Another object of the invention is to provide means for attaching a sabot and a bourrelet to a subcaliber projectile with only slight alteration to the projectile. The sabot and the bourrelet may be connected together and are adapted to be released from the core by centrifugal action or by sliding off the core when the projectile leaves the gun barrel.

Another object of the invention is to provide a subcaliber sabot-projectile having a core provided with an axial boss on its rear end for carrying a disc sabot having a central opening for receiving the boss.

In projectiles of the type described, the sabot normally carries a turning band which engages the rifling of the gun barrel to impart rotation to the projectile, and, accordingly, it is desirable to have a high coefiicient of friction between the sabot and the core so as to transmit rotational forces from the sabot to the core without substantial lost motion.

Another object of the invention, therefore, is to provide a sabot projectile having friction means between the sabot and a subcaliber core, the friction means preferably comprising knurling on one of the engaging surfaces of the sabot and core. Either the front surface of the sabot or a rear surface of the projectile core may be knurled so as to take advantage of the force of set back when the projectile is fired. The unknurled surface may be slightly softer than the knurled surface so as to be engraved by the knurled surface when set back forces the two surfaces together.

A further object of the invention is to provide a projectile as described above which is simple to manufacture and is adapted to large quantity production.

These and other objects of the invention will be apparent from the following specification and the accompanying drawings in which FIG. 1 is a side elevation of one form of the projectile shown partly in section;

FIG. 2 is a rear elevational view of the projectile shown in FIG. 1;

FIGS. 3 and 4 are cross sectional views taken on lines 3-3 and 44, respectively of FIG. 1;

FIG. 5 is a longitudinal sectional view of another embodiment of the invention;

FIG. 6 is a longitudinal sectional view of a third embodiment of the invention;

FIG. 7 is a rear elevational view 'of the projectile shown in FIG. 6;

FIG. 8 is a rear elevational view 'of the bourrelet shown in FIG. 6, and

FIG. 9 is a cross sectional view of a modified form of sabot shown in FIG. 5.

In the projectile shown in FIGS. 1 through 4, a steel core '10 having an ogival nose portion 10a is surrounded along most of its length by a bourrelet which is divided into two sleeve parts of dissimilar substances. The forward portion 11 of the bourrelet has longitudinal radial slots 12 cut from the inside diameter leaving an unslotted outer portion 11a, the thickness of which is determined by the breaking strength of the material. The unslotted portion 11a holds the bourrelet together until it breaks under centrifugal stress, as will be described in greater detail presently. Positioned to the rear of bourrelet 11 is the rear bourrelet 14 which has radial slots 15 and an unslotted peripheral portion 15a. The two bourrelets 11 and 14 may be press-fitted on the core or may be attached in any other suitable manner, the forward sleeve 12 preferably being made of plastic or other light weight material, the rear sleeve desirably being composed of steel or its equivalent. The slots in bourrelet 11 may be offset from the slots in the bourrelet 14, as shown.

The interior of the core is hollowed out at 17 for receiving an explosive charge, and a hole 18 is provided in the base of the core to give access to the opening 17. A plug 19 having a shoulder 19a screws into the opening 18, the shoulder 19a serving to hold an annular ring 20 in place against the rear face of the core.

A sabot 22 of steel or other suitable material is mounted on the base of the core 10 and is attached by suitable means, such as screws 23, to the rear end of the bourrelet 14. The sabot is annular in shape and has a rearwardly extending mounting skirt 22a formed with an annular groove 22!; into which the end of the cartridge case (not shown) is crimped in order to hold the projectile in the cartridge case. A turning band 24 is threaded or otherwise secured on the peripheral portion of the sabot in front of the groove 22b, and adjacent to a forwardly directed hollow boss around which the bourrelet partly fits and against which the bourrelet abuts. The abutting end of the bourrelet is dished in FIG. 1 to define an internal annular recess. The correspondingly shaped hollow boss extends into the recess as shown.

When the projectile is fired from a gun, the turning band 24 engages the rifiing in the gun barrel and imparts rotation to the projectile. When the projectile leaves the gun barrel, it is rotating at a high speed and the resulting centrifugal force on the bourrelet portions 11 and 14 causes the latter to break apart at the weakened portions near the cuts 12 and 15. The wind resistance of the sabot causes it to slide rearwardly off the base of the projectile leaving the core to proceed toward its target at high velocity.

It will be apparent that the new sabot-projectile has relatively few parts, all of which may be manufactured at low cost and are easily assembled. The sabot 22 is amply supported to withstand the forces incident to the powder pressure in the gun, and the central opening in the sabot permits loading of the explosive charge in the core chamber 17 after assembly of the sabot and bourrelet, if desired. Also, because of the central opening in the sabot 22, the projectile may be used as tracer ammunition, in which case the tracer jet from chamber 17 will flow through a suitable opening in the base of the projectile and through the sabot opening. The core 10 is supported and centered in the gun barrel along substantially the entire length of the core by the bourrelet 11, 14 and the sabot 22. Rotation of the sabot 22 by turning band 24 is transmitted to the core 10 through the interengaging faces of the core and sabot, which may be roughened to provide greater friction, and also through the screws 23 and bourrelet 14-. [In this connection, when the gun is fired, the resulting force of setback in the projectile compresses the base of the projectile against the plate 20 and sabot 22, so that the increased friction between these parts causes transmission of torque from the sabot to the core with little or no lost motion.

With the new construction, as shown, the bourrelet 14 and the sabot 22 form in effect a cup for snugly receiving the rear end portion of the core 10. The side wall 14 of the cup, being made of light weight, frangible material, is easily broken and released from the core under centrifugal force during the initial flight of the projectile and after the part 14 has served its purpose of centering the core in the gun barrel, while the heavier sabot 22 is quickly released from the core by the wind resistance to the outer portion of the sabot when the projectile emerges from the gun barrel. The release of the sabot and the bourrelet 111, 14 is effected without substantially influencing the flight stability of the core 10.

Another embodiment of the invention is shown in FIG. and comprises a metal core 26 having an ogival nose portion 26a and a cylindrical boss 26b extending axially from the rear end of the core. A disc sabot 30 of steel or other suitable material is mounted on the boss and has an axial opening into which the boss is closely fitted. A turning band 32 formed of annealed copper or other suitable material is mounted on the periphery of the sabot and has internal tongues 32a disposed in annular grooves in the sabot to hold the turning band. The turning band may be pressed, shrunk or otherwise mounted on the sabot. A bourrelet 27 of plastic or other light weight material is press fitted to the body of the core 26 forward of the sabot and has a plurality of longitudinal radial cuts 28 extending from its inside diameter to a distance from the outside diameter determined by the breaking strength of the material.

In order to transmit rotation from the turning band 32 to the core 26 through the disc sabot 30, without substantial lost motion, we provide friction means operable under the force of set back to resist relative rotational movement between the sabot and the core. As shown, the rear face of the core 26 is knurled around the boss 26b to provide a roughened surface 31 engaging the front face of the sabot disc, the latter being of softer metal than the core so that the force of set back resulting from firing the projectile causes the knurling 31 to engrave the adjacent face of the sabot and thereby provide a more positive means of transmitting the torque from the sabot to the core. The knurling 31 may be made after or during the turning of boss 26b. It will be understood that the knurling, if desired, may be made on the front face of sabot 30, in which case the knurling is hardened so that it is adapted to engrave the softened rear face of the projectile core.

When the projectile shown in FIG. 5 is fired from a gun, the bourrelet 28 breaks apart due to centrifugal force when the projectile leaves the gun, barrel, and the sabot slides rearwardly off the boss 26!; due to the wind resistance of the sabot.

The embodiment shown in FIGS. 6 through 8 comprises a steel core 34- having an ogival nose portion 34a and a rearwardly extending boss 34b formed on the rear end of the core. Closely surrounding this boss is a sabot 38 of steel or other suitable material having longitudinal radial cuts 39 extending inwardly from the periphery so as to leave an inner uncut portion 38a. The segments formed by the cuts 39 are held together by a copper turning band 42 having internal tongues 42a pressed into grooves in the periphery of the sabot 38. In order to insure a substantially gas-tight seal, copper wire 43 is beaten into the cuts 39 in the sabot 38. The sabot 38 has a skirt 41 which extends forwardly from the sabot and engages the rear end portion of the core 34, over which the skirt may be press fitted. A bourrelet 35, which is made of a light weight material, such as plastic,

is press fitted about the projectile and about the sabot skirt 41, the bourrelet having an annular internal recess in its rear end portion for receiving the skirt 41. The bourrelet has longitudinal radial cuts 36 extending outwardly from its inner diameter and leaving an uncut peripheral portion 35a.

The operation of the projectile shown in FIGS. 6 through 8 is similar to that of the projectiles previously described, except that when the projectile emerges from the gun muzzle, the turning band 42 is adapted to fracture under centrifugal force incident to the high speed of rotation of the projectile, with the result that the centrifugal force causes the sabot 38 to break apart near the cuts 39. Accordingly, the sabot 38 is released automatically from the core by either centrifugal action or wind resistance, or by a combination of both. The sabot skirt 41 acts as an additional centering and supporting means for the core in the gun barrel and also aids in the transmission of torque from the sabot to the core. At least one of the interengaging surfaces of the sabot and core is roughened as shown in FIGS. 6 and 7. The complementary member is of relatively softer metal so that its surface will be engraved upon setback to increase the friction between the parts and thereby reduce lost motion in the transmis sion of torque.

In FIG. 9 we have illustrated a modified form of the sabot shown in FIG. 5. The sabot 30a is provided with an axial opening 45 for closely receiving the boss 26b on the rear end of the projectile. A skirt 47 extends forwardly from the front face of the sabot to facilitate attachment to the projectile, the skirt performing the same functions as the skirt 41 shown in FIG. 6. A turning band (not shown) is attached to the periphery of the sabot 30a by means of parallel grooves 46 into which portions of the turning band are press-fitted.

It will be seen that the invention provides means for mounting an easily detachable sabot and bourrelet on a sub-caliber projectile core without substantial alteration to the projectile. The bourrelets of the various forms illustrated, and the sabot and turning band of the form shown in FIG. 6, are so designed, as by means of the radial cuts, that their strengths are substantially exceeded by the centrifugal bursting forces to which they are subjected after emerging from the gun muzzle, so that there is an ample margin of certainty in their release from the core.

We claim:

In a sub-caliber projectile having a sub-caliber core, a sabot mounted on the rear end portion of the core and slidable longitudinally off the rear end of the core, the sabot projecting a substantial distance radially from the core for supporting the core in a gun barrel, a bourrelet of full caliber mounted on the core in front of the sabot consisting of sleeves of dissimilar materials, one of the sleeves being located adjacent the nose of the core and having longitudinal radial cuts, a second sleeve, located between the sabot and said one sleeve and having longitudinal radial cuts offset laterally from said first cuts, and a turning band on the sabot operable to rotate the core through the sabot and the bourrelet.

References Cited in the file of this patent UNITED STATES PATENTS France July 27, 1936 

